The subject invention relates to tape winding and packing at high speeds and includes packs of wound tapes having parallel co-planar tape edge sides.
In all tape drive systems both magnetic and optical, transverse or helical scan, and longitudinal, mono reel and dual reel, a limiting design factor is the ability to wind the tape media at high speed onto the reels in a smooth and consistent layer. A satisfactory tape pack is achieved only when the edges of successive tape wraps or windings onto a reel or otherwise into a pack are in the same plane. Misalignment of tape onto the reel, giving a scattered tape pack, typically leads to inadequate tape guiding on the next wind cycle through the tape transport and often results in problems due to media misalignment during read/write operations. An initially poor tape pack is inevitably followed by increasingly poor tape packing during successive tape winds until a severe pack scatter condition prevails. At low speed, adequate tape packing is generally not a serious problem and various techniques are traditionally implemented to provide the desired smooth tape pack. These techniques include tape edge guiding, reel flange packing, or active steering of the tape direction. In the former the tape media is guided by one of several means to force one tape edge against a stationary guiding block. These include edge top pressure via spring fingers, wedged guides, wedged air guides, or rollers rotating about axes radial to the axis of rotation of the tape pack and rotating on the tape pack at about the same speed as the tape pack itself.
Increasing tape speeds result in poor tape packing and require increasing forces to control the resultant larger amplitude tape displacements and tracking errors, leading to greater tape edge wear rates with correspondingly greater debris generation rates.
In flange packing, the system is constructed so that the medium is guided onto and constrained by a flange on the reel into which the tape is being fed. Active steering involves sensing of the tape path and inputting corrective signals to a tape support member driven by an actuator. This latter approach is complex and each of the first two approaches requires tape edge contact and inherently leads to tape edge damage after a number of winds/rewinds especially as the tape speed increased. Substantial reduction or elimination of edge damage due to many passes through a tape transport is particularly important where a large amount of data is contained on a single tape and is desired to be archived and then accessed many times. A high number of accesses can lead to rapid tape edge wear and damage, both of which eventually lead to the inability to successfully move tape and consequent tape transport malfunction. Many forms of tape edge guiding produce heat which leads to stretching of the tape beyond its elastic limit. This produces waviness at tape edges referred to as xe2x80x9cmarcelling.xe2x80x9d Such wavy part fails to contact the recording and playback heads properly for perfect recording and playback. Without proper guidance, tape tends to ride up on reel flanges during rapid winding, which also produces misalignment of tape relative to recording and playback heads.
In optical systems the tape wear situation is aggravated by the microscopic edge wear debris contaminating the tape data surfaces, leading to interference with data recording and recovery and increased bit error rates.
On the basis of conventional logic, the prior art identified air entrainment between the layers of tape on the take-up reel as the major destabilizing effect in high speed tape winding processes, and as primarily responsible for tape scattering in the resulting tape pack. In consequence, the prior art increased tape tension with increasing tape speeds in an effort to squeeze trapped air from in between all layers of tape forming in the tape winding process. As the industry moved in the direction of thinner tapes in the interest of greater volumetric efficiency, the increasing tape tensions of the prior art came to tax the physical strength of the tape, either stretching the tape beyond tolerable limits or restricting the maximum allowable tension and thereby increasing the amplitude of the pack scatter for a given tape speed.
In its search of a way out of this dilemma, the prior art resorted to packing devices for squeezing the air out of the pack. Both rotating and non-rotating devices have been used. These devices are often loaded against the outer diameter of the growing tape pack with a spring. The major drawback of this prior-art approach is that the incoming tape is locked by traction to the previous layer of tape in the lateral position of its approach, independent of whether that position is co-planer with the previously reeled layers of tape or not.
As the industry moves toward higher tape speeds in the interest of higher data transfer rates and faster data access times, the problem of pack scatter increases accordingly. Work along conventional methods of correcting pack scatter would require the application of greater and greater controlling forces to correct greater amplitude scatter at higher tape speeds. As controlling forces increase, damage to the tape resulting from these controlling forces increases. At high reeling speeds, pack scatter would overwhelm conventional methods of correction. Under some conditions, high tape tension and winding-to-winding misalignment can cause at least temporary and sometimes even a permanent distortion of the tape, thereby affecting if not destroying its information recording, storage and reproducing capability. Under extreme conditions, pack scatter will cause successive windings of tape to be hard packed against the upper reel flange and the lower reel flange. Unwinding tape from this extreme condition can cause further damage to the tape as the tape drags against the upper and lower reel flanges. Without tape flanges, and under certain conditions even with flanges, extreme pack scatter can cause tape to xe2x80x9cjumpxe2x80x9d off a reel resulting in a jammed tape condition or a broken tape.
Scattered tape packs are particularly vulnerable to damage during handling and transport. Layers of tape which are unsupported by the edges of neighboring layers of tape are prone to be crushed, resulting in permanent tape damage.
It is a general object of the invention to overcome the above mentioned prior-art impasse with a break-through solution:
It is a germane object of the invention to provide superior tape winding techniques and systems.
It is a related object of the invention to produce and to enable production of superior tape packs whose radial opposite sides are perfectly co-planar and ideally are of mirror-like quality throughout thousands of reruns.
It is also an object of the invention to enhance information, storage and reproduction capability of tape media beyond prior state of the art feasibility.
Other objects of the invention will become apparent in the further course of this disclosure.
From one aspect thereof, the invention resides in a method of winding tape having opposite edges into an increasing tape pack about an axis of rotation, and more specifically resides in the improvement comprising, in combination, floating substantially each newly arriving winding of the tape on a fluid film on the increasing tape pack, establishing a substantially fluid-free tape pack wherein substantially all corresponding opposite edges of substantially all tape windings in the tape pack are co-planar along opposite radial planes of that tape pack, by continuously aligning opposite edges of substantially each new winding of the tape for a number of turns with corresponding edges of substantially all preceding windings of tape in the increasing tape pack with the aid of the fluid film, while gradually diminishing increments of that fluid film between the turns to zero until each leading turn of the number of turns has become locked to a remainder of the tape pack.
The invention resides also in packs of wound tape having perfectly co-planar tape edges at opposite radial sides of the packs, as produced by the method of the invention or by embodiments thereof at tape speeds in excess of three meters per second.
From a related aspect thereof, the invention resides in apparatus for winding tape having opposite edges into an increasing tape pack about an axis of rotation, and more specifically resides in the improvement comprising, in combination, an interwinding fluid film former coupled to the tape and through substantially each newly arriving winding of that tape for a number of turns at the tape pack, a tape edge aligner at substantially each of the newly arriving windings of the tape and fluid film formed at the increasing tape pack for the number of turns, and a tape winding locker coupled to each leading turn of the number of turns.
From a more specific aspect thereof, the invention resides in apparatus for winding tape having opposite edges into an increasing tape pack about a hub of a tape reel having an axis of rotation, comprising, in combination, the flexible reel flanges on opposite sides of the hub, an interwinding fluid film former coupled to the tape and through substantially each newly arriving winding of that tape for a number of turns at the tape pack, a tape edge aligner at substantially each of the newly arriving windings of the tape and fluid film formed at the increasing tape pack, and a tape winding locker coupled to each leading turn of the number of turns, with the tape edge aligner and tape winding locker including the flexible reel flanges and a continuous reel flange flexer coupled to these flexible reel flanges.